Practical application of hybrid electric vehicles (HEVs) equipped with an engine and an electric motor-generator (hereinafter, referred to as “MG”) has advanced in recent years. One type of HEV is equipped with a toroidal continuous variable transmission (hereinafter, referred to as “T-CVT”). In a T-CVT, an input disc and an output disc are disposed coaxially, and therefore the transmission is short in the radial direction of the discs, but it is long in the axial direction. Therefore, it is difficult to install a T-CVT in a vehicle in which the power train system is disposed in a transverse direction. Consequently, power train systems have been proposed wherein mountability is improved by eliminating the forward/reverse switching mechanism and torque converter, and hence reducing the length of the transmission. For example, JP-A-2002-104000 discloses a drive system wherein an MG and a T-CVT are disposed in parallel, and the vehicle is driven in reverse by using the MG as a drive source.